Unit 1 Body Systems Key Words cell chest function system convert circulate In this unit you will learn to: describe the levels of biological organization. identify the basic structures and functions of the digestive system. identify the basic structures and functions of the circulatory system. identify the basic structures of the respiratory system and explain respiration. make predictions in an independent research experiment. 8 Unit 1
What Do You Know? Initial Evaluation Go to Cutout 1 on page 165. Glue the names of the organs in the correct boxes. 1. Mark the function of each organ listed with a. Allow air to enter and exit the body Pumps blood to other parts of the body Heart Lungs Stomach Helps digest food Scientific Skill: Predict 2. A scientist observes the following in a lab: Situation 1 Situation 2 The mouse has a normal digestive tract. The mouse has an irregular digestive tract. a. Circle the difference between the digestive tracts of the mice. b. What are the possible side effects of an irregular digestive tract? (Situation 2) Life Science 9
Section 2 The Digestive System Connecting The Organs of the Digestive System Have you ever wondered what happens to food after you swallow it? Where does it go? How is it used? The answers to these questions are related to one of the systems in our bodies: the digestive system. This system consists of a group of organs that convert food into nutrients and eliminate what we do not need. The digestive organs surround the digestive tract, which starts at the mouth and ends at the anus. This system also includes a group of digestive glands. The glands secrete various substances that convert food into nutrients. Nutrients give our bodies the energy we need to live. pass from the mouth to the stomach produce and emit Look at the following image of the digestive system. Pay attention to all the organs. Salivary Glands: produce saliva. Mouth: the opening of the digestive tract. Esophagus: a tube that is about 30 centimeters long and connects the mouth to the stomach. Stomach: a muscular organ that produces gastric acid. Liver: produces bile. Pancreas: produces pancreatic acid. Large Intestine: the last part of the digestive system, which eliminates waste. Small Intestine: a sixmeter-long tunnel that connects to the stomach. It absorbs nutrients. The digestive system consists of the digestive tract and digestive glands. Its purpose is to convert food into nutrients, which give us energy. 18 Unit 1
Identify the basic structures and functions of the digestive system The Digestive Process Our digestive system converts food into simpler substances called nutrients, which enter our cells and give us the energy we need to live. This process, called the digestive process, consists of four stages, which occur in the following order: ingestion: when food enters the mouth digestion: the transformation of food in the digestive tract absorption: when nutrients enter the blood egestion: the elimination of waste through the anus Practicing 1. Label each organ of the digestive system. Identify Did You Know...? Nutrients are components of food that give energy to an organism. They also help regulate and repair the body. Nutrients are classified as: carbohydrates, found in foods like bread; proteins, found in foods like eggs; lipids and fat, found in oils; and vitamins and minerals, found in fruits and vegetables. 2. Put the stages of the digestion process in order. Sequence egestion digestion ingestion absorption Summarizing The digestive system allows the body to absorb nutrients and eliminate waste. The stages of the digestive process are: ingestion, digestion, absorption and egestion. Life Science 19
Section 2 / The Digestive System Connecting The Beginning of the Digestive Process As you already know, the digestive process consists of four stages: ingestion, digestion, absorption and egestion. Ingestion is the first stage, and it begins the moment you start to eat. Put a piece of bread in your mouth, but do not chew. Wait one minute, and then chew and swallow it. Did you notice any change in the food? This is because digestion begins in the mouth. Teeth are used to chew food and break it down into smaller pieces. Salivary glands in the mouth produce saliva. The tongue moves and mixes the food with the saliva. All these processes make a bolus, a ball of food ready to be swallowed and to continue down the digestive tract. Remember! Each animal s teeth are adapted to the type of food it eats. A carnivore has long, sharp teeth to rip meat, while herbivores have large, flat teeth to chew plants. bite repeatedly with the teeth tongue teeth salivary glands The mouth, teeth, tongue and saliva all work together to convert food. Why can t babies eat solid food? 20 Unit 1
Identify the basic structures and functions of the digestive system Swallowing Take a sip of water. Did you notice what happens in the back of your mouth? The process of moving liquid from the mouth to the stomach is called swallowing. Swallowing consists of two stages. The first stage is voluntary and occurs when we push food to the back of the mouth. The second stage is involuntary and occurs when the food enters the digestive tract and moves down the esophagus to the stomach. esophagus bolus Peristaltic Movements We have talked about food moving through the digestive tract. How does this happen? The esophagus expands and contracts to push the bolus down to the stomach. These movements are called peristaltic movements. becomes smaller Practicing 1. Put a small ball inside a tube that has the same diameter as the ball. Use your fingers to squeeze the tube and push the ball to the other side. If the ball represents the bolus, what does the tube represent? What movement are you demonstrating with your hands? Explain. Interpret Swallowing is a mechanism that allows food to enter our bodies. After the food is swallowed, peristaltic movements help push the food through the digestive tract. Summarizing Ingestion is the first step of the digestive process. Digestion begins in the mouth when food is converted into a bolus and pushed down the esophagus. Peristaltic movements move the food through the different organs of the digestive system. without curves Word Focus Diameter is the length of a straight line passing through the center of something from one side to the other. In this case, it is the thickness of the tube. Life Science 21
Section 2 / The Digestive System Connecting Digestion in the Stomach: The Process Continues Does your stomach ever make noises after you eat? Or have you ever heard your stomach growling when you are hungry? This happens because the stomach is a muscular organ shaped like a bean, with walls that move to help process food. The bolus of food moves through the esophagus to reach the stomach. Then it goes through a valve located at the entrance of the stomach. This valve is called the cardiac sphincter. Its function is to allow food to pass through to the stomach and to prevent stomach contents from entering the esophagus. When food gets to the stomach, it mixes with gastric juices. Gastric juices help with digestion the transformation of food into nutrients. For example, proteins are digested in this process. Gastric juices and peristaltic movements convert the bolus into a thick liquid called chyme. This liquid then moves toward the small intestine. bolus Word Focus The word growl normally describes the sound a dog makes when it is angry. Growl also means the noise your stomach makes when you are hungry! A sphincter is a ringshaped muscle that regulates the passage of substances from one place to the next. esophagus cardiac sphincter gastric juices stomach chyme Staying Healthy small intestine It is important not to eat too much of certain foods like chocolate or spices. Some foods can have negative effects on the cardiac sphincter, pushing food and gastric juices back into the esophagus. The stomach is a very important part of the digestive system. Its movements and gastric juices help convert food into nutrients. 22 Unit 1
Identify the basic structures and functions of the digestive system The End of the Digestive Process We have already seen that, with the help of the stomach, the bolus is converted into a thick liquid called chyme. The digestive process continues as this liquid leaves the stomach through a valve called the pylorus sphincter and enters the small intestine. The most important part of digestion happens in the small intestine with the help of different fluids. They are: bile, produced by the liver; pancreatic juice, produced by the pancreas; and intestinal juice, produced by the small intestine. Through the action of these juices, the chyme becomes a thinner liquid called chyle. This is the last transformation of nutrients before the third stage of the digestive process: absorption. pylorus sphincter small intestine chyle liver pancreas Practicing 1. Complete the diagram by writing how food changes in each stage. Identify mouth stomach small intestine 2. Explain the functions of the stomach and the small intestine during digestion. Explain Summarizing Tip In these terms, ph is pronounced as f, and ch is pronounced as k. The stomach has walls made of muscle to move and digest the food. It also produces gastric juices that help make chyme. The small intestine produces intestinal juices, which combine with bile (from the liver) and pancreatic juice (from the pancreas) to help make chyle. Life Science 23
Section 2 / The Digestive System Connecting Absorption After the chyle is formed, it continues through the small intestine and the next stage of the digestive process starts: absorption. During this process, most of the nutrients and water go through the small intestinal wall. Small hairs called villi allow the nutrients to reach the blood, which carries them to all the cells of the organism. The intestinal villi on the walls of the intestine increase the efficiency of absorption. In fact, if we could extend all the villi of a human being, they would cover an area of 300 square meters, about the area of a tennis court. The following image shows the structures involved in absorption. associated with Did You Know...? A human s small intestine can be seven meters long, the same as the width of a professional soccer goal. Tip Villi is pronounced vil-lie. The singular form is villus. small intestine blood vessels This close-up of the small intestine s wall shows the villi that allow nutrients to reach the blood, which then carries them to all the cells in the body. What would happen if there were no villi in the small intestine? digestive system lymphatic vessels intestinal villi smooth muscle lymphatic vessels blood vessels close-up of the small intestine small intestinal villi The villi are very important in the absorption process. For example, every day our small intestine receives six liters of chyle, which is reduced to one liter after absorption. Do you know what happens to the rest? It passes through the bloodstream to reach all the cells, providing the organism with basic materials and energy. 24 Unit 1
Identify the basic structures and functions of the digestive system Elimination of Waste: The Final Process We have seen how our digestive system converts food into nutrients, but what happens to the things we cannot use? To answer this, we turn to the large intestine, which comes after the small intestine. After all the nutrients are absorbed, the leftover waste passes to the large intestine. In the final stage of the digestive process, the large intestine forms and eliminates fecal matter in a process called egestion. The large intestine absorbs any water, giving fecal matter its firm consistency. Finally, the fecal matter is temporarily stored in a part of the large intestine called the rectum. Then with the help of bowel movements, it is expelled through a final sphincter: the anus. accumulated Did You Know...? Intestinal flora is the bacteria that live in our intestines. They are necessary for healthy intestines and a healthy body. Staying Healthy Eating a variety of food and an adequate quantity of vegetables contribute to a healthy digestive system. Foods that are high in fiber are especially good for our digestion. large intestine cecum appendix rectum The large intestine forms and eliminates fecal matter as the final stage of the digestive process. anus Life Science 25
Section 2 / The Digestive System Practicing 1. A study measured the amount of food circulating in different areas of the digestive tract from ingestion to egestion. Look at the table and answer the following questions. Digestive Tract Content of an Animal Part of the Tract Mouth Stomach Small Intestine Large Intestine Amount of Food (grams) 490 490 80 70 a. What happened to the amount of food as it circulated through the digestive system? Interpret b. According to the table, where does the most absorption occur? Interpret 2. Go to Cutout 2 on page 165. Glue each organ according to its function. Identify Helps with the absorption of nutrients. Absorbs water and eliminates fecal matter. Summarizing Absorption is when nutrients pass from the digestive tract to the bloodstream. Absorption occurs through the villi in the small intestine. The large intestine absorbs water and forms fecal matter. 26 Unit 1
Identify the basic structures and functions of the digestive system Quiz Yourself 1. Look at the diagram and do the activities. a. Match each part of the digestive system with the correct word. Then describe its function. b. On the diagram, draw arrows to show the path of food through the digestive system. Mouth: Esophagus: Stomach: Large Intestine: Small Intestine: 2. What would happen if food passed directly from the stomach to the large intestine? Life Science 27
Science Lab Scientific Skill: Predict The Function of Saliva Basic Framework The digestive system converts food into more simple substances called nutrients. These nutrients give us the energy we need to live. To be able to convert food into energy, the digestive system consists of several organs, each with a specific function. The digestive process starts in the mouth, with the help of teeth and saliva. Saliva is a secretion containing amylase, which breaks down food starches. Starch is a nutrient found in potatoes, corn and dough. Observation liquid produced by an organ A group of students conducted an experiment in a laboratory. They observed two samples: one of potato and saliva and another of potato and water. One changed color when povidone or Lugol s iodine (antiseptic solutions) was added. Why do you think the colors are different? Research Question destroying bacteria What is the effect of saliva on food? Hypothesis Mark the correct hypothesis for the research question. Amylase breaks down food starch into simpler substances. Amylase does not have any effect on food starch. Predictions Based on the situation described in the observation stage, answer: a. What will the saliva do to the potato? How do you formulate predictions? Based on a situation, answer the questions. To answer, use your hypothesis and any previous knowledge you might have. The questions guide you in formulating a prediction. Your prediction helps you answer the questions. 28 Unit 1
Make predictions in an independent research experiment Experimental Procedure 1. In groups of four students, collect the following supplies: collect reduced to small strips 1 grated potato Lugol s iodine (or povidone) water 2 syringes (without the needles) 2. Gather some saliva in your mouth and extract it with a syringe. Be careful: The syringe should not have a needle. 3. Mark the test tubes A and B with the marker. 2 test tubes 1 marker 1 teaspoon 1 dropper 4. Follow the steps for each tube as indicated in the diagram: Evidence of amylase s activity appears because Lugol s iodine, a special coloring, recognizes food starches. If the food has starches, the color will change from brown to blue. Use one of the syringes to extract saliva and the other to add water to the test tubes. step 1 Add a teaspoon of grated potato and 5 ml of water. step 1 Add a teaspoon of grated potato and 5 ml of water. step 2 Add 3 ml of saliva and wait 15 minutes. A B step 2 Add 3 ml of water and wait 15 minutes. step 3 Add two drops of Lugol s iodine and shake the tube gently. step 3 Add two drops of Lugol s iodine and shake the tube gently. 5. Observe the initial color of each tube and mark it in the Results section. 6. Wait 15 minutes and observe any changes in color. 7. In this experiment, why did you add three more milliliters of water to tube B? Life Science 29
Science Lab Results Use the space below to record the results. a. Draw what happened to tube A when you added Lugol s iodine. Mark the color of the content in tube A before and after you added Lugol s iodine. Initial Color A brown blue Final Color brown blue b. Draw what happened to tube B when you added Lugol s iodine Mark the color of the content in tube B before and after you added Lugol s iodine. Initial Color B brown blue Final Color brown blue 30 Unit 1
Make predictions in an independent science experiment Interpreting and Analyzing the Results 1. What differences are there between the results from tube A and tube B? Remember to think about the change in color of each solution. 2. What do you think caused the difference in color between tube A and tube B after adding Lugol s iodine? In tube A: In tube B: 3. Which observation proves that saliva breaks down starch? Conclusions 1. Did the experiment prove the hypothesis? Explain. 2. What function does amylase serve in the digestion of food like potatoes? 3. Why is it important to break down the starch in foods? Look at the Basic Framework to help you answer. 4. What other foods can you use in this experiment? Explain. Use the Basic Framework to help you answer. Life Science 31
Let s Check! 1. Go to Cutout 3 on page 167 (levels of biological organization). Follow the instructions. : a. Write the name of each level. b. Determine the order of the levels. c. Carefully glue the pictures in the correct order. points 8 Level 1 Level 2 Level 3 Level 4 Level 5 d. Which level of biological organization includes all the other levels? e. What is the first and smallest level of organization? f. In which level would you classify bones? Explain. 32 Unit 1
Unit 1 Intermediate Evaluation 2. Determine which stage of the digestive process is represented in each photograph and in which organ the stage occurs. points 8 Situation Stage Organ ILUSTRACION PENDIENTE Life Science 33
What Did You Learn? 1. Identify the level of biological organization shown in each image. points 5 2. Complete the following table. points Level of Biological Organization Characteristics of the Level Examples 10 Level 1 Level 2 Level 3 Level 4 Level 5 52 Unit 1
Unit 1 Final Evaluation 3. Match each image with the correct description. points 4 This organ absorbs nutrients. This organ produces bile to help digestion. This organ helps eliminate waste. This organ produces gastric juices to help digestion. 4. Fill in the blanks with the correct words. chyme pylorus sphincter esophagus mouth egestion points 5 a. The bolus forms in the before swallowing. b. The is located between the stomach and the small intestine. c. The bolus passes from the mouth to the stomach through the. d. After it passes through the stomach, food is called. e. The process of eliminating waste is called. 5. Complete the table. points Veins Arteries 4 Are the walls thick or thin? Does the blood go to the heart or to the organs? Life Science 53
6. Complete the diagram. points Blood 8 consists of are their function is their function is their function is 7. Which of the following statements about the human heart is correct? A. It expands and contracts to pump blood. B. It is located under the lungs. C. It contracts voluntarily. D. It is a tissue. 8. Complete the following diagram showing the path of air from the nasal passage to the alveoli. point points 1 5 nasal passage alveoli 54 Unit 1
Unit 1 9. Complete. a. The movement that forces air out of the lungs is called. points 5 b. In the alveoli, the absorption of oxygen and elimination of carbon dioxide occurs through. c. The primary organs of the respiratory system are the. d. To allow air to enter the body, we need to. e. The oxygen we need comes from the. Scientific Skill: Predict 10. The following image shows gastric bypass surgery. This surgery is for people who suffer from severe obesity. Look at the image and answer the question. points 3 bypass stomach small intestine Using what you have learned in this unit, how can people who have this surgery absorb nutrients? Find Test 1 Study Page Life Science 55